The TMSR-500 is a "Thorium Molten Salt Reactor" nuclear power plant being designed for the Indonesia market by ThorCon. The TMSR-500 is based on a small modular reactor (SMR) that employs molten salt technology. The reactor design is based on the Denatured molten salt reactor (DMSR) design from Oak Ridge National Laboratory and employs liquid fuel, rather than a conventional solid fuel. The liquid contains the nuclear fuel and serves as primary coolant. ThorCon plans to manufacture the complete power plants cheaply in shipyards employing modern shipbuilding construction techniques.
ThorCon proposed to use modular shipbuilding production processes in a shipyard to build each TMSR-500 as a completed power station. The TMSR-500 would then be floated and towed on the ocean to the installation site where the walls would be filled with concrete or sand as ballast and shielding. Notably the setup of rebar is not required in this process as steel plate construction provides the concrete reinforcement and is integral to the hull design.
The power plant consists of a nuclear fission section and a steam/electrical section. The fission section of the plant consists of two power modules, each with two siloed reactor units of which only one is active at any time. The operational reactor units each generate 557 MW (thermal) yielding 250 MW (electric). This means the overall plant with two active reactors can yield 500 MW (electric). Each reactor unit operates for four years, cools for four years, and is then replaced. Such retired reactors use passive cooling to remove decay heat until they are cool enough to be replacement. Any fuel recycling would occur offsite.
The reactors operate at near-ambient pressure reducing steel requirements by 50% and concrete requirements by 80% versus a conventional nuclear plant. Little of the concrete must be reinforced. In the event of a reactor overheating thermal expansion of the salt stops the fission reaction and if necessary triggers freeze valves to drain the reactor and separating the fuel from the moderator. Hazardous fission products iodine-131, cesium-137 and strontium-90 are chemically bound in the reactor salt preventing their release.
The steam/electrical section features the same design and cost ($700/kw) of a 500 MWe coal plant. A 1 GWe nuclear component requires less than 400 tons of supercritical alloys and other exotic materials.
In addition to (low cost) thorium, a 1 GWe reactor initially requires 3,156 kg of 20% low enriched uranium along with 11 kg per day of operation. Every 8 years the fuel must be changed out. At a yellowcake cost of $66/kg, a $7.50 UF
6 conversion cost and $90 per separative work unit, the levelized fuel cost is 0.53 cents per kilowatt-hour.
Every 8 years 160 tons of spent fuel travel to the recycling facility, consisting of about 75% thorium, with 95% of the balance uranium. Without separation (other than removing the salt), the total fuel waste stream averages about 2 m3 per year.
A 2017 study by the Energy Innovation Reform Project looked at the TMSR-500 and concluded that "if power plants featuring these technologies are able to produce electricity at the average LCOE price projected here (much less the low-end estimate), it would have a significant impact on electricity markets.".